Two-Dimensional δ5 Borophene Monolayer with High Specific Capacity for K-Ion Batteries: A First-Principles Study

Potassium-ion batteries (KIBs) have drawn considerable research interest due to their excellent safety and the rich reserve of K. Although there have been great breakthroughs in KIB technology, exploring promising anode materials of KIBs is still a challenge. The development of high-performance two-dimensional anode materials is crucial for applications of KIBs. Here, by first-principles calculations, we find out a desirable anode material, a metallic δ5 borophene monolayer with a low diffusion barrier of 0.117 eV, a low average open-circuit voltage of 0.416 V, and a high storage capacity of 1549.37 mA h g–1. Such crucial characteristics make δ5 borophene a promising candidate for anode materials of KIBs.